1. Field of the Invention
The present invention relates generally to hand-operated printing devices and, more particularly, to a hand-operated printer which may be conveniently used to print machine-readable ZIP code information on letters and parcels prior to mailing.
2. Description of the Prior Art
The volume of mail now being processed by postal services in the United States and other countries creates significant delays in the delivery of mail, often resulting in considerable inconvenience. In order to speed the delivery of mail and reduce associated costs of processing mail, many postal systems are turning to automated sorting equipment. Applications of such automated sorting equipment are described in "Mail-Sorting System Reads Typed Addresses and Verifies ZIP Codes", Electronics, Dec. 21, 1978, pages 60-61. In one such system, typed mailing addresses are optically scanned, and the resulting image is processed by a computer in order to select a ZIP code and associated postal destination from the typed address. Upon verifying that the ZIP code and postal destination are in agreement with each other, the automated system marks letters and postcards with fluorescent ink in a bar code format. The bar code is subsequently used by sorting equipment to route the mail into the proper destination bins.
The automated sorting equipment described above has several disadvantages. First, such systems require that the address be typed upon the letter or postcard. However, many postal system users do not own a typewriter, nor can they afford to purchase one. In addition, those postal system users who do own a typewriter would find it inconvenient to carry the typewriter along with them in order to write letters while away from the home or office. Secondly, such optical scanning equipment is very expensive and is subject to errors due to lack of uniformity in the format of the typed addresses. Errors may also be caused by smudged characters or the presence of foreign matter upon the letter in the vicinity of the typed address.
Magnetic ink has been widely used on bank checks to allow high speed machine processing of such checks. It is anticipated that magnetic ink may be used in the future for addressing mail to permit similar high speed machine processing of the mail.
Irregardless of whether postal services standardize upon optical scanning of addresses formed with conventional ink or machine reading of addresses formed with magnetic or other special ink, it is clear that address information should be in a standardized format in order to increase the efficiency of the automated sorting equipment.
A stamping device for impressing ZIP codes upon envelopes and the like is disclosed in U.S. Pat. No. 3,370,531. The device disclosed by the above mentioned United States patent includes a plurality of pinion wheels having cog gear teeth and a corresponding plurality of rack bars engaging the cog gear teeth for selecting the ZIP code to be printed. A pair of ink pads are disposed on opposite sides of the pinion wheels for inking the numerals carried thereon when the pinion wheels are rotated in either direction. Although the pinion wheels of the device disclosed by the above mentioned United States patent are shown having eleven cog gear teeth for printing the numerals 0-9, the disclosure states that twenty-seven such teeth may be used where the English alphabet is being imprinted.
Although the above mentioned prior art ZIP code stamper allows a ZIP code to be printed in a standardized format, it suffers from several disadvantages. First, the use of ink pads for inking the raised type characters on the pinion wheels results in printed characters of inconsistent density and clarity. An excess of ink deposited upon the raised type characters may cause the printed character to become blurred or smudged. On the other hand, when the pinion wheels are not rotated between successive printings, as would be true when the same or similar ZIP codes are being printed on several letters in succession, the raised type characters on the pinion wheels eventually lack sufficient ink to clearly print the selected character. In addition, the ink pads must be removed and replaced whenever a user desires to replenish the ink supply or to change the type of ink being used. The requisite handling of the ink pads at such times is necessarily a messy and time-consuming chore.
Another disadvantage of the prior art ZIP code stamper described above regards the difficulty which is encountered in modifying the printing mechanism to provide the letters of the English alphabet. If the number of cog gear teeth on a pinion wheel were increased from eleven to twenty-seven, the circumference of the pinion wheel, and correspondingly its diameter, would increase by a factor of 2.5. Similarly, the rack bar used to turn the pinion wheel would also be lengthened by a factor of 2.5. Thus, the overall dimensions of the prior art ZIP code stamper would be greatly increased, whereby the ZIP code stamper would become bulky and inconvenient to use. This consideration is particularly significant in view of a proposal by the United States Postal Service to adapt a nine-character ZIP code to more completely specify the address of the sender wherein the nine-character format may include alphabetical characters as well as numerals.
Another feature of the prior art ZIP code stamper which may be considered disadvantageous is the use of rack bars for selecting the characters to be printed. Many potential users of such a ZIP code stamper would prefer a means for selecting the characters to be printed which the user can manipulate with a single finger or thumb. Ideally, such a ZIP code stamper would also accommodate use by the blind.
To ensure a high degree of print quality, a ZIP code printer should be provided with a means for holding or clamping the letter or other article to be imprinted to prevent any movement of the letter or article during the printing process. Ideally, the article to be imprinted would be clamped only during the actual printing process in order to avoid interfering with insertion and withdrawal of the article to be imprinted from the ZIP code printer.
Accordingly, it is an object of the present invention to provide a printer adapted for printing ZIP codes in a standardized format wherein the printer is compact, convenient to use, and inexpensive.
It is another object of the present invention to provide a printer adapted for printing ZIP codes wherein the need for withdrawing and replacing ink pads is eliminated.
It is another object of the present invention to provide a printer adapted for printing ZIP codes wherein the printed characters have a sharpness and density of that customarily obtained only by using an inked ribbon.
Another object of the present invention is to provide a printer adapted for printing ZIP codes wherein the printing ink can be replenished or changed quickly and conveniently.
Still another object of the present invention is to provide a printer adapted for printing ZIP codes wherein both numerical and alphabetical characters may be printed while maintaining the printer as a compact unit.
It is another object of the present invention to provide a printer adapted for printing ZIP codes wherein a user can manipulate the means for selecting the characters to be printed with a single finger or thumb.
It is a further object of the present invention to provide a printer adapted for printing ZIP codes which can be used by people who are blind.
It is a still further object of the present invention to provide a printer adapted for printing ZIP codes which securely clamps the article to be imprinted during the printing process without interfering with the insertion of the article into the printer or the withdrawal of the article from the printer.